People use oral zinc to help treat colds, but it can decrease the effectiveness of certain drugs and cause side effects.

The recommended daily amount of zinc is 8 milligrams (mg) for women and 11 mg for adult men.

Evidence

Research on oral zinc for specific conditions shows:

Zinc deficiency. People who have low levels of zinc appear to benefit most from zinc supplements. This kind of deficiency isn't common in the United States.

Colds. Evidence suggests that if zinc lozenges or syrup is taken within 24 hours after cold symptoms start, the supplement can help shorten the length of colds. However, use of intranasal zinc has been linked with the loss of the sense of smell, in some cases long term or permanently.

Diarrhea. Oral zinc supplements can reduce the symptoms of diarrhea in children with low levels of zinc, such as from malnutrition. There isn't enough evidence to recommend use of oral zinc for children with diarrhea who have a healthy, varied diet.

Age-related macular degeneration. Research suggests that oral zinc might slow the progression of this eye disease.

Zinc that's used topically is known as zinc oxide. Zinc oxide cream, ointment or paste is applied to the skin to prevent conditions such as diaper rash and sunburn.

Our take

Generally safe

Oral zinc supplements might benefit people with low levels of zinc. Taken soon after cold symptoms appear, zinc might also shorten the length of a cold.

However, don't use intranasal zinc, which has been linked with the loss of the sense of smell.

5 Tips: Natural products for the flu and colds: What does the science say? National Center for Complementary and Integrative Health. https://nccih.nih.gov/health/tips/flucold.htm. Accessed Aug. 8, 2017.

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